NASHVILLE - As days get shorter and nights become chillier, the annual fall foliage show is getting under way in the Southeast.

The first colors are beginning to show in the higher elevations of the Great Smoky Mountains National Park, which is a popular draw for tourists in October.

Expect a good show, said Janet Rock, a botanist in the Smokies.

"As long as we stay on track with the weather we've had, it should be a good year," she said.

The shorter span of sunlight each day is the main trigger, but Rock said temperatures and precipitation also affect the show.

"When you have warm sunny days and nights that don't reach freezing, it brings out the best colors," Rock said.

The mountains weren't affected badly by drought conditions that burned crops to the west.

Leaves change color because they're shutting down photosynthesis, which makes food for the trees. The production of green chlorophyll masks other colors. However, red pigment production also ramps up as photosynthesis shuts down.

TENNESSEE: COLOR TEASING

Smokies spokeswoman Molly Schroar noted yellow birch, American beech, mountain maple and hobblebush have begun turning high in the mountains, giving a hint of the rich show to come. But Shroar suggested looking down now and then to see black-eyed Susans, purple asters, goldenrod and other fall flowers just hitting their peak.

"We're getting teased a little bit by Mother Nature now," said Cindy Dupree of the Tennessee Department of Tourism as she looked out her car window at hits of red sumac and golds in the maples. "It won't be long until it's spectacular."

"On down in the Chattanooga area, that gets just as pretty as I've seen anywhere," Dupree said.

GEORGIA: DOGWOODS VIVID

The North Georgia mountains typically showcase some of the state's brightest fall colors, and this year will be no exception, state forestry officials say.

Dogwood and maple trees in the upper elevations already have begun to change color, Ken Masten, a district manager with the Georgia Forestry Commission, wrote in a recent report.

"If we get a cold snap in the next two weeks or so where it gets 15 or 20 degrees colder, then the colors will be a little more vivid," said Joe Burgess, a senior forester with the Georgia Forestry Commission.

The colors are a big draw in North Georgia's mountain towns, where tourists come to see the hues of the leaves and then stay to shop or catch some live music at venues such as the Crimson Moon Cafe in Dahlonega, 60 miles north of Atlanta.